ULTRA HIGH STRENGTH COLD ROLLED STEEL SHEET WITH EXCELLENT SPOT WELDING AND FORMING CHARACTERISTICS, ULTRA HIGH STRENGTH PLATED STEEL SHEET AND METHOD FOR THEIR MANUFACTURE Russian patent published in 2023 - IPC C21D8/04 C22C38/60 C22C38/32 C22C38/38 C22C38/28 C22C38/22 C21D9/46 C23C2/06 C23C2/28 

FIELD: metallurgy.

SUBSTANCE: invention is related to cold-rolled steel sheet with a tensile strength of 820 MPa or more, used in the automotive industry. The sheet is made of steel containing, in wt.%: from 0.05% to 0.09% carbon (C), from 0.5% to 1.0% silicon (Si), from 2.0% to 2.8 % manganese (Mn), 0.2% to 0.5% aluminium (Al), 0.8% to 1.2% chromium (Cr), 0.05% to 0.10% molybdenum (Mo) , 0.03% to 0.06% titanium (Ti), 0.001% to 0.003% boron (B), 0.02% to 0.05% antimony (Sb), 0.001% to 0.015% phosphorus (P), more than 0% to 0.003% sulphur (S), 0.004% to 0.006% nitrogen (N), and the rest being iron (Fe), as well as irreducible impurities, and has a microstructure containing ferrite and martensite, having an average hardness of 4.5 GPa or less.

EFFECT: sheet has high weldability characteristics during spot welding and forming.

20 cl, 9 dwg, 7 tbl